Michael Tokarev wrote:
Single Seagate 74Gb SCSI drive (10KRPM)
BlkSz Trd linRd rndRd linWr rndWr linR/W rndR/W
4k 1 66.4 0.5 0.6 0.5 0.6/ 0.6 0.4/ 0.2
2 0.6 0.6 0.5/ 0.1
4 0.7 0.6 0.6/ 0.2
16k 1 84.8 2.0 2.5 1.9 2.5/ 2.5 1.6/ 0.6
2 2.3 2.1 2.0/ 0.6
4 2.7 2.5 2.3/ 0.6
64k 1 84.8 7.4 9.3 7.2 9.4/ 9.3 5.8/ 2.2
2 8.6 7.9 7.3/ 2.1
4 9.9 9.1 8.1/ 2.2
128k 1 84.8 13.6 16.7 12.9 16.9/16.6 10.6/ 3.9
2 15.6 14.4 13.5/ 3.2
4 17.9 16.4 15.7/ 2.7
512k 1 84.9 34.0 41.9 33.3 29.0/27.1 22.4/13.2
2 36.9 34.5 30.7/ 8.1
4 40.5 38.1 33.2/ 8.3
1024k 1 83.1 36.0 55.8 34.6 28.2/27.6 20.3/19.4
2 45.2 44.1 36.4/ 9.9
4 48.1 47.6 40.7/ 7.1
<snip>
The only thing I don't understand is why with larger I/O block
size we see write speed drop with multiple threads.
Huh? Your data table does not show larger block size dropping write
speed. 47.6 > 38.1 > 16.4.
And in contrast to the above, here's another test run, now
with Seagate SATA ST3250620AS ("desktop" class) 250GB
7200RPM drive:
BlkSz Trd linRd rndRd linWr rndWr linR/W rndR/W
4k 1 47.5 0.3 0.5 0.3 0.3/ 0.3 0.1/ 0.1
2 0.3 0.3 0.2/ 0.1
4 0.3 0.3 0.2/ 0.2
16k 1 78.4 1.1 1.8 1.1 0.9/ 0.9 0.6/ 0.6
2 1.2 1.1 0.6/ 0.6
4 1.3 1.2 0.6/ 0.6
64k 1 78.4 4.3 6.7 4.0 3.5/ 3.5 2.1/ 2.2
2 4.5 4.1 2.2/ 2.3
4 4.7 4.2 2.3/ 2.4
128k 1 78.4 8.0 12.6 7.2 6.2/ 6.2 3.9/ 3.8
2 8.2 7.3 4.1/ 4.0
4 8.7 7.7 4.3/ 4.3
512k 1 78.5 23.1 34.0 20.3 17.1/17.1 11.3/10.7
2 23.5 20.6 11.3/11.4
4 24.7 21.3 11.6/11.8
1024k 1 78.4 34.1 33.5 24.6 19.6/19.5 16.0/12.7
2 33.3 24.6 15.4/13.8
4 34.3 25.0 14.7/15.0
Here, the (total) I/O speed does not depend on the number
of threads. From which I conclude that the drive does
not reorder/optimize commands internally, even if NCQ is
enabled (queue depth is 32).
While the difference does not appear to be as pronounced as with the WD
drive, the data does show more threads give more total IO. 4.7 > 4.5 >
4.3 in the 64k rndRd test, and the other tests show an increase with
more threads as well.
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